XMLHttpRequest: stop truncating responses at the first NUL byte

Polyfills/XMLHttpRequest/Source/XMLHttpRequest.cpp

@@ -121,7 +121,8 @@ namespace Babylon::Polyfills::Internal
     {
         if (m_request.ResponseType() == UrlLib::UrlResponseType::String)
         {
-            return Napi::Value::From(Env(), m_request.ResponseString().data());
+            const std::string_view responseString{m_request.ResponseString()};
+            return Napi::String::New(Env(), responseString.data(), responseString.size());
         }
         else
         {
@@ -134,7 +135,12 @@ namespace Babylon::Polyfills::Internal
 
     Napi::Value XMLHttpRequest::GetResponseText(const Napi::CallbackInfo&)
     {
-        return Napi::Value::From(Env(), m_request.ResponseString().data());
+        // The body may legitimately contain embedded nulls: Emscripten's EXPORT_ES6 output, for
+        // example, inlines the .wasm payload as a JavaScript string literal. Passing .data()
+        // alone would hand a const char* to Napi and truncate at the first null, so the length
+        // has to be supplied explicitly.
+        const std::string_view responseString{m_request.ResponseString()};
+        return Napi::String::New(Env(), responseString.data(), responseString.size());
     }
 
     Napi::Value XMLHttpRequest::GetResponseType(const Napi::CallbackInfo&)

Tests/UnitTests/Scripts/tests.ts

@@ -291,6 +291,14 @@ describe("XMLHTTPRequest", function () {
         const vertexCount = parseInt(/element vertex (\d+)\n/.exec(header)![1]);
         expect(vertexCount).to.equal(18713);
     });
+
+    it("should not truncate responseText or response at an embedded null byte", async function () {
+        const xhr = await createRequest("GET", "app:///Assets/embedded_nulls.txt");
+        expect(xhr.status).to.equal(200);
+        expect(xhr.responseText).to.equal("start\0middle\0end");
+        expect(xhr.responseText.length).to.equal(16);
+        expect(xhr.response).to.equal(xhr.responseText);
+    });
 });
 
 describe("fetch", function () {